1. Field of the Invention
The present invention relates to a lifter for lifting a heavy load and, more particularly, to such a lifter, which is safe and durable in use.
2. Description of the Related Art
When lifting weights in a narrow place where a tower host or crane is not workable, a lifter may be used. Various lifters have been disclosed. There is known a lifter, which is comprised of a lifting main unit, a motor, and a transmission gearbox. The lifting main unit comprises an outer tube, and a telescopic tube mounted in the outer tube. The telescopic tube is formed of three inner tubes that slide one inside another. Each inner tube has the top and bottom sides respectively mounted with a pulley. The gearbox is coupled to the motor and adapted to rotate a winch, causing the winch to roll up or let off a cable, which has one end fastened to the winch and the other end extended in proper order through the pulleys at the top and bottom sides of each inner tubes and then fixedly connected to the bottom side of the last inner tube. When starting the motor to turn the transmission gear of the gearbox forwards/backwards, the winch is driven to roll up/let off the cable, thereby causing the telescopic tube to be extended out of or received inside the main tube. This structure of lifter is not safe in use. If the cable broke during operation, the lifter becomes unworkable, and an accident may occur. Further, because notches are made in the main tube and the inner tubes for accommodating the pulleys. The structural strength of the tubes is weakened.